1. Field of the Invention
The present invention relates generally to lifting devices, and more particularly, to a wheelchair lift device to provide access to stages, platforms, risers and other elevated structures for individuals with disabilities.
2. Description of the Background Art
Under the Americans With Disabilities Act of 1990 (the “ADA”), the U.S. government required that public buildings be accessible to the disabled. For persons requiring a wheelchair for mobility, abrupt changes in floor elevation have to be modified to enable access by wheelchair. The ADA permits vertical lifting devices to be used instead of a ramp.
Lifting devices for the disabled are known in the prior art. For example, U.S. Pat. No. 5,105,915 (Gary) describes a lifting device having a car including fixed sides and short, one-piece ramps at each end. The car is raised and lowered by a pantograph jack including a hydraulic pump driven by an electric motor controlled by switches. The patent also describes several lifting devices of the prior art. Another wheelchair lifting device is disclosed in U.S. Pat. No. 6,182,798 to Brady, et al., and assigned to AGM Container Controls, Inc., the assignee of the present invention. The '798 patent discloses a lift device with gates at both ends of the lift car, transparent walls, a loading ramp, a dock plate, a stage height sensor, and numerous safety features. In addition, U.S. Pat. No. 7,926,618, also assigned to the assignee of the present invention, discloses a lift device suitable for elevating wheel chair-bound individuals to stages or platforms.
Wheel chair lift devices are often used repeatedly in conjunction with the same stage or platform, whereby the lift car is elevated numerous times to the very same height. It is therefore desirable to provide a control mechanism by which the maximum elevational height of the lift can be set in advance, or programmed, thereby automatically stopping the lift at the stage height repeatedly and consistently. The wheel chair lift device disclosed in assignee's prior U.S. Pat. No. 7,926,618 discloses a height adjustment mechanism accessible through a panel of the lift car for varying the elevational height of the lift. A rotatable arm is used to set the elevational height, and a knob secured to the end of such rotatable arm slides within a circular slot. The knob can be loosened to move the knob within the circular slot, thereby repositioning the rotatable arm. Once the knob is set to the desired elevational height, the knob is re-tightened, and the access panel is closed.
An alternate height adjustment mechanism is disclosed in assignee's U.S. Pat. No. 7,721,850 for use with a fixed-installation lift, wherein a cable attached to an actuator moves the actuator as the lift car moves, the actuator eventually engaging a microswitch when the lift reaches the desired maximum height. Adjustment of the maximum desired height requires an installer to adjust the relative position of the microswitch along a rail traversed by the actuator.
Portable wheelchair lifting devices generally require that the height to which the lift car is elevated be readily adjustable. Such lift devices are frequently moved from one stage or platform to another, and the elevations of two or more stages or platforms often differ from one another. On the other hand, once a portable lift is transported to a particular location, and the maximum height has been re-adjusted to suit the particular platform or stage at the new location, further height adjustments are neither required nor recommended.
Therefore, it is important to be able to quickly and easily adjust the maximum height to which the lift is elevated each time the lift is moved to a different platform or stage. Once the maximum height is set for the new stage or platform, it is also important that the lift should be able to raise the platform of the lift device repeatedly, and reliably, to the pre-set maximum height. Clearly, it would be advantageous to be able to verify that the mechanism used to signal that the maximum height has been reached is, in fact, operational before permitting the lift car to elevate; if the maximum height detection system is not working properly, and the lift is permitted to be elevated, the lift will not automatically stop when it reaches the desired maximum height.
In view of the foregoing, it is an object of the present invention to provide a wheel chair lift device suitable for lifting wheelchair-bound users up to the height of stages, platforms, risers and the like in a safe and reliable manner, and comporting with all applicable ADA requirements.
Another object of the present invention is to provide such a lift device that is relatively inexpensive, easy to construct and use, and simple to maintain.
A further object of the present invention is to provide such a lift device wherein the maximum height to which the lift car is raised can be quickly and easily adjusted for allowing the lift device to be repeatedly raised to the height of the platform with which the lift device is currently being used.
A still further object of the present invention is to confirm that the control system used to halt further elevation of the lift car, upon reaching the selected maximum height, is operational before the lift car is significantly elevated.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.